traverse / parse a XML file in Java with DOM Parser example code . XML document / file Parsing using recursion

XML - a Markup Language which defines structured and platform-independent data that can be exchanged between different applications and platforms. Both XML and Java technology helps for developing Web services and applications that access Web services. Extensible Markup Language (XML) also supports Unicode encoding . Such things made XML to become such a great and popular technology very quckly. . As XML is used every where , it is very important for java developers to read / access / parse XML document in java programming.
To work with XML in Java and XML Parser, Developer needs to have basic knowledge of XML document. It is necessary to know the terms like tags, elements, attributes and nodes of XML document for parsing the XML.
Tags : tag is the text between the left (<) and right (>) angle brackets . Starting tags are represented as <tagname> and ending tags are represented as </tagname>
Elements : An element is the starting tag, the ending tag, and tags in between them. Elements have children that may be other elements, text nodes, or a combination of both. Example for elements in the below sample books xml are <book>, <title>, <author> , <year> are elements.
Attributes : XML elements can have attributes which provide additional information about an element. eg. <book id=“954”> , id is as attribute
Nodes : Everything in an XML document is a node. Elements are only one type of node. We can call the whole document as document node , each XML element as element node , the text in the XML elements as text node , Every attribute as attribute node , Comments as comment node . In the below books xml document , books is the root node , which has two book nodes , whereas each book node has three nodes such as title , author and year and each of them have text node.

The following is the sample XML document to represent the Books details.

 <?xml version="1.0" encoding="UTF-8"?><books><book id=“954”> 
       <title>Effective Java</title> 
       <author>Joshua Bloch</author> 
       <year> 2009 </year></book><book id=“777”> 
           <title>Effective Java</title> 
           <author>Scott Meyers</author>
           <year> 2010 </year>
       </book></books>
Tree Representation of above XML Books

Another sample XML document to represent the Employee details with Salary
    <EmpDetails>         <Employee>             <Name>ABC</Name>             <Designation>ABC</Designation>             <Scale>50000-200000</Scale>             <Salary>                   <Basic>121199.00</Basic>                   <HRA>20000.00</HRA>                   <TA>10000.00</TA>              </Salary>           </Employee>           <Employee>              <Name>XYZ</Name>              <Designation>ABC</Designation>              <Scale>12100-100000</Scale>              <Salary>                    <Basic>21199.00</Basic>                    <HRA>2000.00</HRA>                    <TA>1000.00</TA>              </Salary>           </Employee>       </EmpDetails>

XML parser checks syntax . XML document can have an optional Document Type Definition (DTD), called Schema which defines the XML document structure. If the XML document adheres to the structure of the DTD , then it is valid .

Now let us see how to access and use an XML document through the Java programming language. Two ways are there
1. Through parsers using the API Java API for XML Processing (JAXP)
two parsers are provided with the above API .
i) Simple API for XML (SAX)
ii) Document Object Model (DOM).
2. Through the new API Java Architecture for XML Binding (JAXB).
3. Using JDOM an open-source API
4. Using Apache Xerces

In our tutorial , we are going to parse the above books and Employees XML files using DOM Parser.
Java developers can make use of DOM parser in an application through the JAXP API . DOM parser creates a tree of objects that represents the data in the whole document and puts the tree in memory. Now the program can traverse the tree , to access / modify the data.

Steps to Parse XML file using DOM Parser

1.Create a document factory for DOM methods to obtain a parser that produces DOM object trees from XML documents.
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); which creates a new factory instance.

 2. Create document builder to obtain DOM Document instances from an XML document.
DocumentBuilder db = dbf.newDocumentBuilder(); which creates a new instance of a DocumentBuilder . XML can be parsed using the instance of this class.

3. Get the DOM Document object by parsing the content of the given XML file as an XML document
Document dom = db.parse(books); which returns DOM object where books is an XML file. Other input sources accepted by parse method are InputStreams, Files, URLs, and SAX InputSources.

4. Access / manipulate the XML document using various methods

Some of the useful methods to get nodelist , elements , node , node value , etc ...

To get the node list of all the elements from the document by giving the tag name .
NodeList nodes = dom.getElementsByTagName("book"); where book is the tag name. Nodes are returned by traversing Document tree by preorder traversal

To get the single node item from the above nodelist . The items in the NodeList are accessible through index, starting from 0.
Node node = nodes.item(index);

To get the element node of the given node .
Element element = (Element) node;

To get all child nodes of the above element for a particular tag
NodeList nodes = element.getElementsByTagName("title").item(0).getChildNodes(); - where title is the tag.

To get the children of root node .
Element root = doc.getDocumentElement(); // gets the root node.
NodeList children = root.getChildNodes(); // returns the children of root.

To get at node information , getNodeName() , getNodeValue() can be used .

Tree struture can be traversed using recursion easily . The following code traverses the entire Book XML document and prints all node names and values if exisit using recursion . This code can traverse any XML.
    import java.io.File;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import org.w3c.dom.*;public class DOMParser1 {public static void main(String args[]) {try {File books = new File("books.xml");DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();Document doc = dBuilder.parse(books);doc.getDocumentElement().normalize();Element root = doc.getDocumentElement();  // gets the root element bookxml_traverse_DOM(root);} catch (Exception ex) {    ex.printStackTrace();}}private static void  bookxml_traverse_DOM(Node element)   {      System.out.println(element.getNodeName()+" = "+element.getNodeValue());         for (Node child = element.getFirstChild(); child != null;  child = child.getNextSibling())      {                     bookxml_traverse_DOM(child);                    } }}

The following code (partly) can be used to find the value (text node) of the tags title , author , year of books.xml
    NodeList bookNodes = doc.getElementsByTagName("book"); // all book nodesfor (int i = 0; i < bookNodes.getLength(); i++) {    Node bookNode = bookNodes.item(i);  if (bookNode.getNodeType() == Node.ELEMENT_NODE) {          Element element = (Element) bookNode;              System.out.println("Book Title: " + getTextNode("title", element));          System.out.println("Author Name: " + getTextNode("author", element));          System.out.println("Year of Publishing: " + getTextNode("year", element));            }     } getTextNode methodprivate static String getTextNode(String tag, Element element) {NodeList nodes = element.getElementsByTagName(tag).item(0).getChildNodes();Node node = (Node) nodes.item(0);return node.getNodeValue();  // returns the only one text node value. }
 Output:

Now let us parse the above Employees XML and calculate the Total salary of each employee without using recursion .
    import java.io.File;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import java.io.*;import org.w3c.dom.*;public class employees_DOM {   public static void main(String[] args) {         try{     File employees = new File("emp.xml");     DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();     DocumentBuilder db = dbf.newDocumentBuilder();     Document doc = db.parse(employees);     doc.getDocumentElement().normalize();         // get all the employee nodes         NodeList employeeNodeList = doc.getElementsByTagName("Employee");         for(int i=0; i<employeeNodeList.getLength(); i++) { double total_salary=0.0;             Node employeeNode = employeeNodeList.item(i); // one employee node at a time    NodeList employeeChildNodeList = employeeNode.getChildNodes();    // all child nodes of employee node                        for(int j=0; j<employeeChildNodeList.getLength(); j++) {                                   Node employeeChildNode = employeeChildNodeList.item(j);   //Name , Designation , Scale ,Salary ....                                     if (employeeChildNode.getNodeType() == Node.ELEMENT_NODE) {                 String employeeChildNodeName=employeeChildNode.getNodeName();                  Node employeeTextNode = employeeChildNode.getFirstChild();//the only text node                 int no_of_childs=employeeChildNode.getChildNodes().getLength();    // no of childs inside name  child , designation , ..., salary  . salary has more than one child nodes.                 if (no_of_childs==1)                  System.out.println( employeeChildNodeName + "  = " +employeeTextNode.getNodeValue().trim());   else    {   // samething for salary  node    NodeList salaryChildNodeList = employeeChildNode.getChildNodes();   // all child nodes of salary node         for(int k=0; k<salaryChildNodeList.getLength(); k++) {                                      Node salaryChildNode = salaryChildNodeList.item(k); //  to get  basic , hra, ta ...                                        if (salaryChildNode.getNodeType() == Node.ELEMENT_NODE) {                    String salaryChildNodeName=salaryChildNode.getNodeName();                     Node salaryTextNode = salaryChildNode.getFirstChild(); //the only text node                       System.out.println( salaryChildNodeName + "  = " + salaryTextNode.getNodeValue().trim());      total_salary=total_salary + Double.parseDouble(salaryTextNode.getNodeValue().trim());      }      }      }      }              }   System.out.println("Total Salary = " + total_salary + "\n");           }      }  catch (Exception e) {e.printStackTrace(System.err);}       }}
 Output:

Some of the imporatnt uses of XML :
XML is used everywhere , some of the example are given below
 1. XML plays big role in Webservice through messaging. XML and Web services architecture allows applications written in different languages on different platforms to exchange information with each other in a standards-based way.
2. XML helps to create interactive pages that allows the customer to customize those pages which can be translated to XHTML using XSL stylesheet. With XML,the data is stored once and can be rendered for different viewers with different style based on the style sheet which is processed by XSLT ( Extensible Style Language Transformation ).
3. Ajax helps to communicate with server applications with the help of XML
4. Many configuration files used by Application Server , Framework are xml .
 5. XML helps to keep the data separated from your HTML

Java Interface Concepts and core use of interface in Java

Interface in java is core part of its programming language despite that many programmers thinks Java Interface as an advanced concept and refrain using interfaces from early in programming career. At very basic level  interface  in java is a keyword  but same time it is an object oriented term to define contractsand abstraction , This contract is followed by any implementation of Interface in Java. Since multiple inheritance is not allowed in Java,  interfaceis only way to implement multiple inheritance at Type level. In this Java tutorial we will see What is an interface in Java, How and where to use interface in Java and some important points related to interface in Java.

Key Points about Interface in Java

1. Interface in java is declared using keyword interface and it represent a Type like any Class in Java. a reference variable of type interface can point to any implementation of that interface in Java. Its also a good design principle to "program for interfaces than implementation" because when you use interface to declare reference variable, method return type or method argument you are flexible enough to accept any future implementation of that interface which could be much better and high performance alternative of current implementation. similarly calling any method on interface doesn't tie you with any particular implementation and you can leverage  benefit of better or improved implementation over time.

2) All variables declared inside interface is implicitly public final variable or constants. which brings a useful case of using Interface for declaring Constants. We have used both Class and interface for storing application wide constants and advantage of using Interface was that you can implement interface and can directly access constants without referring them with class name which was the case earlier when Class is used for storing Constants. Though after introduction of static imports in Java 5 this approach doesn't offer any benefit over Class approach.

3) All methods declared inside Java Interfaces are implicitly public and abstract, even if you don't use public or abstract keyword. you can not define any concrete method in interface. That's why interface is used to define contracts in terms of variables and methods and you can rely on its implementation for performing job.

4) In Java its legal for an interface to extend multiple interfaces. for example following code will run without any compilation error:

interface Session extends Serializable, Clonnable{ }

here Session interface in Java is also a Serializable and Clonnable. This is not true for Class and one Class can only extend at most another Class. In Java one Class can implement multiple interfaces. They are required to provide implementation of all methods declared inside interface or they can declare themselves as abstract class.

Example of interface in Java

Java standard library itself has many inbuilt interfaces like Serializable, Clonnable, Runnable or Callable interface in Java.  Declaring interface is easy but making it correct in first attempt is hard but if you are in business of designing API then you need to get it right in first attempt because its not possible to modify interface once it released without breaking all its implementation. here is an example of declaring interface in Java :

 interface SessionIDCreator extendsSerializable, Cloneable{
        String TYPE = "AUTOMATIC";
        int createSessionId();
    }
 
    class SerialSessionIDCreator implements SessionIDCreator{

        private int lastSessionId;
       

 @Override
         publicint createSessionId() {
            return lastSessionId++;
        }
    
    }

In above example of interface in Java, SessionIDCreator is an interface while SerialSessionIDCreator is a implementation of interface. @Override annotation can be used on interface method from Java 6 onwards, so always try to use it. Its one of those coding practice which should be in your code review checklist.

When to use interface in Java

Interface is best choice for Type declaration or defining contract between multiple parties. If multiple programmer are working in different module of project they still use each others API by defining interface and not waiting for actual implementation to be ready. This brings us lot of flexibility and speed in terms of coding and development. Use of Interface also ensures best practices like "programming for interfaces than implementation" and results in more flexible and maintainable code. Though interface in Java is not the only one who provides higher level abstraction, you can also use abstract class but choosing between Interface in Java and abstract class is a skill. Difference between Interface in Java and abstract class in java is also a very popular java interview question.

That's it for now on Interfacein Java, specifics of Java interface and How and when to use Interface in Java.  Interface is key to write flexible and maintainable code. If you are not yet using interface in your code than start thinking in terms of interfaces and use it as much possible. You will learn more about interfaces when you start using design patterns. many design patterns like decorator pattern, Factory method pattern  or Observer design pattern  makes very good use of Java interfaces.

Convert String into Int data type and finally convert into DateTime for Compare two dates in C#

Hi
I have two string value and i want to convert into DATETIME so that , i can do difference between them
like below

string a= 07032011 12:50
string b= 07032011 23:40

DateTime aa = new DateTime(int.Parse(a.Substring(4, 4)), int.Parse(a.Substring(2, 2)),
                                         int.Parse(a.Substring(0, 2)), int.Parse(a.Substring(9, 2)), int.Parse(a.Substring(12, 2)),

                                         00);
            DateTime bb = new DateTime(int.Parse(b.Substring(4, 4)), int.Parse(b.Substring(2, 2)),
                                         int.Parse(b.Substring(0, 2)), int.Parse(b.Substring(9, 2)), int.Parse(b.Substring(12, 2)),

                                         00);
    TimeSpan cc = aa - bb;

ind day= cc.days;
int hour= cc.hours;
int minutes= cc.minutes;

UNix Shell script for Oracle database access through Putty

In Latest R&D for Oracle database which is on Unix plateform. Our Team Member access it through Putty below important script for that

1. go to SqlPlus*

  > sqlplus "/as sysdba"

2) to show all user


> show users

3) to all database
>
4) create tablespace

create tablespace ts_something
  logging
  datafile '/dbf1/ts_sth.dbf' 
  size 32m 
  autoextend on 
  next 32m maxsize 2048m
  extent management local;

SQL Query to create xml file from sqlserver 2008

Below Query i have use in my project to create xml file directly through SQL Server 2008 by using SQL Query table column value in CDATA

select 1    as Tag,
       null as Parent,
       AIRPORT_ITEM.

       AIRPORT_ID as [AD!1!AIRPORT_ID!CDATA],
       AIRPORT_ITEM.LEVEL1_TITLE as [AD!1!LEVEL1_TITLE!CDATA],
        AIRPORT_ITEM.XML_BLOCK as [AD!1!XML_BLOCK !CDATA],
        AIRPORT.GENDEC_FLAG as [AD!1!GENDEC_FLAG!CDATA]

    
from AIRPORT_ITEM  join AIRPORT 
 ON (AIRPORT_ITEM.AIRPORT_ID = AIRPORT.AIRPORT)
   
for xml explicit

java.lang.ClassCastException During Deserialization in java

At time of deserialization by below code

FileInputStream out= new FileInputStream("c://ser//ser.txt");

ObjectInputStream outs= new ObjectInputStream(out);

      Employee e=(employee)outs.readObject();

If JVM unable to identify the class type i.e. when outs try to call method readObject and programmer given wrong class reference then it will throw  exception

java.lang.ClassCastException: Serlialization.employee1

WriteReplace method concept during Serialization in Java

WriteReplace method use by JVM during Serialization  to indentify the which object user want to searlize .

Below program for better understanding.

package Serlialization;

import java.io.Serializable;

class employee1  implements Serializable

{

      public String sname="king";

      int a;

      employee1()

      {

           

            System.out.println("superclas constructor run");

      }

      public void getNameEmployee1()

      {

            System.out.println("The employee1 getName Employee1");

      }

      /* public  Object readResolve() {

                System.out.println("Read Resolve method calling");

              throw new RuntimeException();

          }*/

     

}

public class employee  implements Serializable

{

      employee1 e= new employee1();

      String name="kumudg";

      int a;

      int c;

      transient int d;

      transient String password="password";

    static String age="raju";

    private Object writeReplace() {

        //System.out.println("The control in writeReplace method");

    return e;

      //return new SerializationProxy(this);

    }

   /*public  Object readResolve() {

        throw new RuntimeException();

    }*/

  public employee()

 

  {

        System.out.println("Inside the employee object contructor ");

  }

 

 

  public void getName()

  {

        System.out.println("Inside the getName method"+name);

       

  }

     

 

 

 

 

}

Serliaztion Test class

package Serlialization;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.Serializable;

public class serializationTest {

public static void main(String [] args)

{

                serializationTest st= new serializationTest();

                employee e= new employee();

                //employee e=null;

                 st.serializedObject(e);

                //employee de=st.deserializedObject();

                //System.out.println("The value is "+de.name + de.age);

                //System.out.println("The transient value is "+de.password);

    //System.out.println("The transient value is "+de.sname);

               

}

public void serializedObject(employee e)

{

                try {

                                FileOutputStream out= new FileOutputStream("c://ser//ser.txt");

                                ObjectOutputStream outs= new ObjectOutputStream(out);

                                outs.writeObject(e);

                               

                } catch (FileNotFoundException e1) {

                                // TODO Auto-generated catch block

                                e1.printStackTrace();

                }

                catch (Exception e1) {

                                // TODO Auto-generated catch block

                                e1.printStackTrace();

                }

               

}

}

When programmer will serialize object then employee1 class’s object will searlize because the object return by WriteReplace method in Employee class returning object of Employee1